Thursday, July 24, 2014

The Doomsday Argument

There exists something called the Doomsday Argument, and it is considered to be one of the most controversial probabilistic arguments that have been advanced.

Randall Munroe has given a very good summary of the argumentation:
Humans will go extinct someday. Suppose that, after this happens, aliens somehow revive all humans who have ever lived. They line us up in order of birth and number us from 1 to N. Then they divide us divide them into three groups--the first 5%, the middle 90%, and the last 5%:
Now imagine the aliens ask each human (who doesn't know how many people lived after their time), "Which group do you think you're in?"
Most of them probably wouldn't speak English, and those who did would probably have an awful lot of questions of their own. But if for some reason every human answered "I'm in the middle group", 90% of them will (obviously) be right. This is true no matter how big N is.
Therefore, the argument goes, we should assume we're in the middle 90% of humans. Given that there have been a little over 100 billion humans so far, we should be able to assume with 95% probability that N is less than 2.2 trillion humans. If it's not, it means we're assuming we're in 5% of humans--and if all humans made that assumption, most of them would be wrong.
To put it more simply: Out of all people who will ever live, we should probably assume we're somewhere in the middle; after all, most people are.
If our population levels out around 9 billion, this suggests humans will probably go extinct in about 800 years, and not more than 16,000.
He goes on to state that most people immediately conclude that the idea is obviously wrong, but "the problem is, everyone thinks it's wrong for a different reason. And the more they study it, the more they tend to change their minds about what that reason is."

Well, there are two reasons why that could be so. One is that the argument is really quite clever but most people don't realise it. The other is that there is so much wrong with it that people discover new layers of wrongness every time they look at it.

I guess I would have to be counted among those who think that the Doomsday Argument is, indeed, idiotic. Admittedly I cannot come up with a super-deep Bayesian counter-argument such as are referenced in the linked Wikipedia article. But I don't think that is necessary because this does not look like a job for probabilistic reasoning anyway.

Wednesday, July 23, 2014

Another brilliant piece of science spam

Lately I get the feeling that, on average, scientific spam trolling for paper submissions to poor quality, for-profit journals get somewhat sleeker and more professional looking. And perhaps I have now blocked so many of these spammers that I get less of the really obvious ones.

But sometimes a real howler still gets through. Look at this beauty:

Tuesday, July 22, 2014

Botany picture #165: Blackstonia perfoliata

Blackstonia perfoliata (Gentianaceae), south-western France, 2014. This little yellow Mediterranean gentian was all over the place when we visited family in June. Strangely we never noticed it during previous visits to the area.

Monday, July 21, 2014

How to make a bad identification key

Today was my first lecture of the year, and after an introduction to the course as a whole I started with identification tools.

For the non-biologists, I have blogged before about identification keys; the most common type consists of a series of nested questions asking about characters of the organism you are trying to identify. In the style of a choose your own adventure book, answering the questions correctly will ultimately lead to your happy end, in this case the name of the species you are interested in.

Looking over my lecture brought to mind some of my own painful experiences trying to identify plants in the past. (The willow key in the Flora Europaea, argh argh argh...) I may write something more positive soon, for example explain different ways of designing a key or point towards really good examples, but for the moment let's brainstorm a list of what a taxonomist should do if they want to produce a really atrocious key.

To make them as difficult to use as possible, one should:

Thursday, July 17, 2014

So what is so great about Hans Christian Andersen anyway?

I should really write something about plant systematics again, but at the moment something else is going through my head.

My daughter brought a children's book version of The Snow Queen from the library, probably inspired by Frozen. She likes to have it read, but neither I nor my wife can really appreciate the story. If you can call it a story.

So there is this troll who builds a magical mirror that reflects everything in an evil, distorted way, and when he tries to have it reflect the angels of heaven in a negative way, it shatters into thousands of tiny shards. These shards blow around the world and turn people evil who get them into their eyes and hearts. Okay, a mythical explanation for why people can be bad, so far so good. Apart from the fact that the whole story is nauseatingly in-your-face Christian I could live with it.

Next there is this boy called Kai who is infected with two of the shards and turns bad, starting to ignore his close friend Gerda. Again, so far so good. Then in a complete non sequitur the Snow Queen comes and abducts Kai, making him forget all about his previous life. Why? No idea, at least in our version it just happens. And despite the title of the book that is also the last we ever see of that character.

Tuesday, July 15, 2014

Botany picture #164: Teucrium polium

Teucrium polium (Lamiaceae), France, 2014. Interestingly, this widespread Mediterranean species comes in white, yellow and pink varieties. In the south-western part of France where my in-laws are living I have only ever seen the yellow morph.

Monday, July 14, 2014

A few quick things

Currently reviewing a manuscript, and it is so full of hyperbole that I can only stand it in homoeopathic doses, like two paragraphs per day.

If I read "paradigm shift" another time I am going to scream.


Whoever compiled this slide show of photographs from the World Cup Final must be really fond of (1) Bastian Schweinsteiger's girlfriend, (2) Lukas Podolski's son, and (3) sad Argentinean fans. Not sure what that says about their state of mind.


Jason Rosenhouse demolishes the weird idea that until about 150 years ago all Christians saw the bible as merely symbolic and allegoric. Part 1, part 2.

The general problem with holy books is this: They all contain wrong, stupid and hateful things, be it that the world is flat, that the world is a few thousand years old, that insects have four legs, that women should have less rights than men, that adulterers should be stoned, that heretics should be killed, or that holy war is the duty of every believer.

There is no doubt that, believers mostly being decent people, you can have four generations or so of everybody saying, "this is our holy book, it was inspired by the benevolent creator of the universe, you must accept it as a moral compass but please ignore this stuff about a recent creation, about stoning and holy wars".

But, believers being human beings, it is unavoidable that at some point, perhaps in the fifth generation, there will be somebody who reads the book and says, "wait a second, you told me this is our holy book, it was inspired by the benevolent creator of the universe, and I must accept it as a moral compass. But here it says that the world was recently created in pretty much the state it is now." And if you are a bit less lucky, they will say, "but here it says that I should kill the unbelievers, the homosexuals and the adulterers. To prove that I am a more pious person than you, and to gain favour in the eyes of the LORD, I will now do some killing."

As long as texts containing stupid and nasty parts are seen as sacred, peaceful and tolerant religion is not necessarily a stable state of affairs.


This is awesome.